Some households have different companies for water in and water out. Maybe contact Anglian water to find out if you have to pay Independent Water Networks too.
Who are they and do I need to register with them? although I already have an account with Anglian Water who are my supplier and who sent me my monthly payment, water meter number and first meter guestimate. I then had a letter from these people with a direct debit form and priority services explaination leaflet. Anyone else had the same?